What event caused south carolina to secede from the union

The election of Lincoln as President.

While other long-term factors led to South Carolina's secession from the Union, the immediate cause was Lincoln's election to presidency.

so, based on the research i've done. the u.s. government were always on a wild goose chase just to take down castro. he then retired his trone to his brother raul in 2008 due to some health issues. so it's obvious your answer would be:

castro had no allies from which he could receive aid.

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